In quarries and other types of payload material collection sites, mobile loaders, such as wheel loaders, backhoe loaders, and track type loaders are used to load loose payload material into haul vehicles, such as over-the-road trucks. Payload information, including the desired type and amount of payload material for each truck needs to be communicated to quarry personnel who operate the loaders. For instance, this information might be transmitted from a quarry office-based computer to a mobile computer on a loader via wireless communication, as described in co-owned U.S. Pat. No. 5,848,368. This information enables a loader operator to proceed to the correct pile corresponding to the requested material.
A typical work cycle can begin with a loader operator first positioning a bucket of a loader at a pile of a requested material. The bucket is then lowered so that it is near the ground surface. The operator then advances into the pile and controls the bucket to raise the work implement through the pile, fill the bucket and lift the material. The operator then tilts or pitches the bucket back to capture a full bucket load of material. The operator then moves the loader to a desired target location, such as an over-the-road truck, and dumps the captured material from the bucket. The operator then moves the loader back to the pile to start this work cycle again. In the case of typical over-the-road trucks, depending upon their size, a full truck load will typically require between three and six full bucket loads to fill the truck with the desired material to a target load weight.
Many of today's loaders have payload control systems that allow for accurate measurements of the bucket payload. Thus, with each successive bucket, the loader can sum the load weight of the bucket loads to determine or estimate an amount of material already in the truck. Typically on a final pass of the truck loading cycle, the loader operator loads, weighs, and manually discards excess material prior to dumping the bucket load into the truck, to thereby achieve the desired truck target payload weight with a final, partial, bucket load. This process of manually discarding excess material is time consuming and wasteful since it can require trial and error weigh cycles. In the case of a typical over-the-road truck with a target load capacity of about 45 tons, it is difficult for some skilled operators to place an amount of material in the truck that is within 1,000 pounds of that target load, but does not exceed the target load. Less skilled operators require substantially more time through trial and error to fully load a truck without exceeding the target weight, while still being acceptably close to the target payload weight.
After the truck has been loaded, to determine if the truck has a desired amount of payload material therein, the truck is usually driven onto scales and weighed before leaving the quarry or other payload collection site. If the truck is overloaded, some of the payload material must be removed. Alternatively, if the truck is substantially underloaded, more payload material must be added. These processes cost additional time and money.
One strategy for dealing with these precision loading problems is described in co-owned U.S. Pat. No. 6,211,471. In that reference, the loader payload control logic determines that a final pass is needed to bring the truck payload up to a target payload weight. The control logic then controls the loader to retrieve and capture the desired weight of material into the bucket from the pile. Neutralizing the transmission, capturing material at a higher gear, and varying the amount of power available to the engine drivetrain are discussed in the '471 patent as ways to control the amount of material captured with the bucket. The captured material is then dumped into the truck to bring it up to its desired target weight. While this strategy appears to have promise, in practice there is great difficulty in precisely loading a desired weight of material in a bucket, as many variables contribute to, or detract from, the ability to accomplish this task on a reliable and repeatable basis.
The present disclosure is directed to overcoming one or more of the problems or shortcomings set forth above.